In a country where slavery can be as much a psychological state as a physical one, Salimata Lam tackles it holistically.

Salimata Lam is the national coordinator for SOS Esclaves, a Mauritanian association dedicated to fighting modern-day slavery [Ould Youssef/Al Jazeera]

When I got off the plane at the Nouakchott International Airport, I had just flown over miles and miles of the Sahara Desert, looking out of the airplane window at so much endless, timeless sand that the dunes seemed, to my mind, like whitecaps on an ocean.

When I got off the plane at the Nouakchott International Airport, I was landing in a country wholly apart from the place from which I'd come.

Mauritania, in western Africa, is a cloistered kind of country, an Islamic republic with unpaved roads and street corner moneychangers. It is a country that only got its first working ATM in 2004, a country whose television and radio stations are entirely state-owned, a country where, according to UNESCO, 67 percent of adult females can neither read nor write.

At the airport, I looked around and found that I was the only woman there. Since I was there conducting research for my novel, whose female protagonist is an escaped slave who hails from the Mauritanian desert, I found myself wondering where this country's women were, and hoping to meet one who would offer me an insight into the place and its people.

I soon discovered the woman I was looking for: Salimata Lam.

The backbone of anti-slavery

Lam is a slim woman of average height and elegant movement. She was dressed, on the day I met her, in a powder blue mulaffa - the traditional dress of Mauritania. With her soft voice and beatific smile, she might best be described as a presence.

Lam is the national coordinator for S O S Esclaves, a Mauritanian association dedicated to fighting modern-day slavery. It is arguably the country's premiere antislavery organisation, founded in 1995 by Boubacar Ould Messaoud, a dynamic former lawyer who is widely regarded as "the grand-pere of the abolitionist movement".

But Lam is modest and says of her work: "The commitment and trust in the correctness of what one is doing will always give you the courage to do and continue."

Sarah Mathewson, the Africa programme coordinator of Anti-Slavery International, which works with SOS Esclaves to combat slavery, is a little more forthcoming about just what it is Lam contributes: "She is the backbone of SOS Esclaves. She runs the project in a very quiet way behind the scenes. She is very committed to the victims and the work. We can never raise enough money for the salary she deserves, but she just carries on, working all kinds of hours and making all sorts of personal sacrifices to do this work she believes in."

Lam's passion for justice is an asset to a country with a higher prevalence of modern slavery than any other on the planet. According to the Walk Free Foundation's Global Slavery Index, Mauritania, with its population of just 3.8 million, has between 140,000 and 160,000 slaves. That's about four percent of the population, and it is, according to many organisations, including Lam's, a rather conservative estimate: they point to a figure closer to 15 percent.

But slaves are hard to count in a country whose landscape is covered by the drought-wrung, ever-expanding Sahara, even as it is slaves who perform the desert economy's most demanding work: When Lam introduces me to a recently escaped family of slaves, I learn that the young children in the family had been made to herd camels - an especially arduous job in this harsh climate.

And it isn't just the landscape that makes quantifying this problem so difficult. Owing to the caste-based nature of Mauritanian slavery, it also takes on a psychological element. Mauritanians tend to be born into vocations, and 'slave' is one of them. No words feel necessary to describe a condition accepted by so many of those who are born into it, and slaves do not always readily identify themselves as such.

What is more, the Mauritanian government itself maintains a stance of quiet denial regarding the scourge that flourishes within its borders. In 1981, the government became the last in the world to abolish slavery, but slave-owning did not become a punishable offence until 2007.

In August of this year, thanks to the efforts of anti-slavery activists such as Lam, the country doubled the prison term for offenders from 10 to 20 years, and criminalised 10 other forms of slavery, including forced marriage.

Lam notes, however, that to date, only one slaveholder has been conclusively prosecuted for owning slaves, in November 2011, after two boys - aged 10 and 12 - escaped confinement and turned to the Initiative for the Resurgence of the Abolitionist Movement (the IRA). The IRA directed the boys to SOS Esclaves, who took the case to court, and the two boys were able to testify against the man who had held them.

It is not uncommon for slaves to hold what Mathewson calls "a perverse loyalty" to their masters, who exert psychological as well as physical control over them, and the boys' mother actually testified on behalf of the slaveholder.

Nonetheless, the slaveholder was convicted that December, and served four months of a two-year sentence before being released on bail, pending an appeal. That appeal has never taken place, though Anti-Slavery International is part of a coalition that plans to take the case to regional court. The boys are now under the care of SOS Esclaves, although their mother remains a slave.

A handful of other cases have been brought to court and charged with lesser crimes, such as exploiting a minor or kidnapping, but not one of them has seen any jail time - which stands in stark contrast to some of the anti-slavery activists.

According to Lam, she and her colleagues are often followed by Mauritanian government operatives. And in November 2014, three anti-slavery activists - Biram Dah Abeid, Brahim Bilal Ramdane, and Dijby Sow - were convicted of "membership in an unrecognised organisation, taking part in an unauthorised assembly, failing to comply with police orders, and resisting arrest". It is not the first time such high-profile activists have been arrested in a country with a history of detaining and intimidating anti-slavery campaigners.

A holistic fight against social injustice

It is Ramadan when I visit and the temperature in Nouakchott has risen to its typical summer high of somewhere around 43 degrees. Although I have fasted through plenty of holy months since I converted to Islam some 20 years ago, the extreme heat here is making me realise that I may need water.

But, thankfully, when Lam picks me up from my hotel to take me by taxi to the offices of SOS Esclaves, which are in an unassuming white concrete building in a rather quiet part of the city, I quickly learn that she is exactly the kind of person who will offer water before I feel the need to ask for it.

And when the taxi driver asks a probing question about my obvious foreignness, she tells him that I am her petit soeur - little sister - and, having thus graciously dismissed him, begins to explain the city of Nouakchott.

She motions out the window at the passing donkey carts and the men on mopeds during our journey to the office, where she again offers water. She keeps my thick foreign blood well-hydrated.

And this is exactly her approach to combating slavery - kind and thoughtful, yet powerful and effective.

"SOS Esclaves," she explains, "fights for the eradication of slavery through familial descent. We provide recourse for slaves and former slaves, and we raise community awareness about the laws against slavery, and the rights of people under the laws. We make pleas to policymakers to improve the laws and their application. We also provide legal assistance to victims seeking redress."

But Lam, in her position at SOS Esclaves, does so much more than that. She helps people holistically, from the inside out.

When we arrive at the SOS Esclaves offices, which are tucked away on a side street in the capital city, we find a man sweeping the entrance corridor. He is dressed in a polo shirt and slacks, and, with his serene smile and efficient movements, seems quite possibly the happiest sweeper I have ever seen.

"He was a slave," Lam tells me as we head upstairs to her office.

I am shocked that this man with the carefree aura of someone who has spent a lifetime untouched by tragedy was once a slave.

As I spend the day in the SOS offices, I see him do many things - he empties the rubbish, runs errands, brings me more water. He is one of the many former slaves whose lives have been transformed by the job training that Lam coordinates.

At SOS Esclaves, former slaves can learn to style hair, dye clothes, tailor, and cook. Such job training is essential in the caste-based Mauritanian economy, where former slaves often find that once they've escaped, there's no competing in a job market where employment is so firmly bound to ancestry.

Lam's comprehensive approach to helping people transition from slavery to freedom seems entirely appropriate for someone who has long been about the business of assisting others.

She enjoyed what she calls "a very happy childhood" in the village of Boghe, which is in the Brakna region of southern Mauritania along the Senegal River, and says of her paternal grandparents, who housed and educated her: "They made me what I am today."

In 1968, Lam succeeded in entering her sixieme, the first year of secondary school under the French educational system, at the College des Jeunes Filles, and made the move 317km north to Nouakchott to attend.

It was as a young student in Nouakchott that she canvassed for the Mouvement National Democratique, which was founded in 1968 as a semi-clandestine organisation with a left-wing agenda that opposed the domestic policies and foreign alignments of then-President Ould Daddah.

"I learned the fight against social injustices then," she says. "The years passed, but watching social disparities did not desensitise me. I realised that it is only in the defence of human rights that I could find my place, despite the risks."

She started her career teaching the blind, and then moved on to other kinds of human rights work. Along the way, she had four children of her own - two sons and two daughters. When I ask her how she managed to balance career and family, she remains modest. "Like so many women," she says, "I simply try to fulfill my family responsibilities and my work responsibilities without one infringing on the other."

In 2010, she was recruited for the post of national coordinator of SOS Esclaves and happily accepted. "This work," she says, "puts me in direct contact with victims of slavery, particularly with women and children who have experienced a lot of violence and deprivation. They need much accompaniment and support."

A family of freed slaves sit on the floor of a tent as they share their story [Jacinda Townsend/Al Jazeera]

Born free

Even if slavery is hard for the Mauritanian government to quantify and punish, it isn't invisible. It is everywhere you look, if you know what you are looking for. It is there in the darker-skinned woman who sits outside a tent beside a stove while a lighter-skinned family sits inside, fanning themselves. It is in everything you hear, if you know what to listen for. The young girl, no older than 10, who hangs laundry on a roof all morning long, and then goes back inside, only to be heard screaming a few moments later as though she is being beaten.

In the late afternoon, I am driven from the offices of SOS Esclaves to a tent on the outskirts of Nouakchott. There, I meet a woman who has escaped slavery with her eight children - some of whom were fathered by her master, all of whom are the product of rape.

One of the woman's children, a sickly girl who looks to be around the six or seven years of one of my own children, collapses in a fit of coughing. All eight of the children gather to sit on the tent's raffia-matted floor. Unlike my girls, they are perfectly still and perfectly quiet. I ask if I can take a photograph and they oblige.

I close my eyes and hear the wind gathering in the sand; I open my eyes and wonder, since there is obviously no plumbing and no outhouse, how they are bathing and where they go to the toilet.

Lam had arranged for an English-speaking student from the University of Nouakchott to accompany me on the visit, and the happy, sweeping man has come along too. He starts speaking to me in Hassaniya Arabic, and the student begins translating. It turns out that the happy sweeper is the escaped woman's brother. He shares their story.

After his own escape, he began searching for her, he says, but the local government in her region claimed it had no record of her existence. Various emissaries from SOS Esclaves, including Boubacar Messaoud himself, travelled north in search of the woman, but no one could find her in the vast network of dunes and scarps that make up the northern part of the country.

Rural Mauritanians tend to be nomadic - and given the vast area of desert that the search had to cover, no one would have been surprised if it had been abandoned. But the woman's brother persisted. When the man's sister was eventually found, she was eight months pregnant.

She delivered her baby just after escaping, in a city between the site of her rescue and Nouakchott. This baby, who is sleeping so profoundly as we speak, is the first in her family born outside of slavery.

I ask if I can hold her, and as I do, I breathe deeply of her sweetness. As a black American, I'm not that many generations removed from slavery myself. To fight my gathering tears, I focus on the tiny gold earrings in her tiny, delicate ears, and I feel something for which there are no words in the English language. I feel what every slave in every place in all of history felt when he or she saw their first child born free.

After a time, it is overwhelming. The tide of my emotions takes such a physical form that I feel I might wake this dreaming baby. I hand her back to her mother, and I return to taking notes in my small Moleskine notebook.

Later, as I leave the SOS offices, I ask Lam how I can help. "The most important outside aid," she tells me, "is advocacy for significant changes in policy direction".

Write to your own state department, I think to myself. Write to your senator.

"The work of activists and human rights defenders in Mauritania is a difficult job because one must do it at all times. We who defend human rights are investing a lot but faced with many obstacles on the ground. But it remains very meaningful work, and there are always changes. There are no fewer slaves now, but there is all the time a slave who becomes aware of his situation and who dreams of another life with freedom and dignity," she continues.

All the fight in the world

The sun sinks as I tell Lam goodbye, and go on to spend one of the most beautiful evenings of my life at the grand home of Messaoud, who is holding an iftar dinner in the courtyard of his residence. We are covered by a large version of one of the tents that are so customary here in Mauritania. It is cool white on its canvas underside, held up by steel columns that make it as expansive as a sail.

Messaoud and his wife offer course after course of delicious food: succulent vegetables, restorative bissap, chicken that falls off its bone. The guest list for the evening is pure kindness: my translator, his friend, a young female student from Mali, and others who work to communicate with me in French. After a day without food, I feel my body singing at what has been served, but I feel my soul singing too: for what has been served is grace.

I get on a plane the following day and fly back over that sea of high dunes, but the moment I remember as a departure is my descent from Messaoud's SUV, the moment I waved him salaams and told him, over the traditional Mauritanian music he has playing in the tape deck, that I wish SOS Esclaves all the fight in the world.

I walk through the packed sand of the road and the gate of my hotel thinking about the work of Salimata Lam, and how she uses her kindness to assist slaves in their transition from a life in black and white to a life in technicolour.

I leave Mauritania so much more peacefully than I arrived, because now I have seen that there is so very much power in that infinity of sand.